Make publish_data wait until the DataChannel's bufferedAmount becomes low.
#1467
| Job | Run time |
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| 6m 57s | |
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| 7m 31s | |
| 7m 13s | |
| 8m 17s | |
| 3m 54s | |
| 5m 49s | |
| 3m 48s | |
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| 3m 50s | |
| 1h 7m 35s |